News

Sub acute rumen acidosis

Published 18 May 12

Over the last couple of months there have been some articles in
the press about Sub acute rumen acidosis (SARA) in grazing cows.
Piers Badnell, DairyCo extension officer, looks at the facts and
issues behind the condition.

"The articles have explained that good quality grass has high
levels of rapidly fermentable carbohydrates, which lead to a build
up of lactic acid," says Piers Badnell. "This causes the rumen pH
to fall, leading to acidotic conditions. The low fibre levels mean
cows cud less, which in turn reduces the buffering capacity of
saliva. The results of this can mean less milk sold, more
lameness, reduced fertility, extended calving intervals and higher
vet bills.

"The articles state that this potential problem can be avoided
by feeding various yeasts and protected starches and proteins
etc,"he continues.

"The press articles quote a paper that was in the Veterinary
Journal 176 (2008) 44-49 by Luke O'Grady, Michael L Doherty, Finbar
J. Mulligan from the School of Agriculture, Food Science and
Veterinary Medicine, University College Dublin, which is an
excellent piece of peer reviewed work.

"But I think the results of this paper have been taken out of
context and used to promote a product which may well not be
necessary," Piers Badnell explains. "Cows grazing can potentially
be susceptible to SARA, but the incidences are low and the paper
certainly did not say whether feed additives would or would not
help.

"Some of the points in the conclusions of the paper were that
low and sub optimal rumen pH was only found in a sub population of
grazing herds and it questions whether this has an effect on herd
health.

"It also states that there are difficulties in interpreting the
significance of rumen pH," he continues. "The pilot study found no
statistical correlation with problems of animal health, however
some studies showed an association between low rumen pH and
lameness negative energy balance and infertility, note an
association not direct cause and effect.

"The paper suggested that further studies are needed into;

the incidence of SARA in grazing cows

understand rumen pH variation at grass

the prevalence of SARA in grazing cows between herds and other
stages of lactation as this study only focussed on peak dry matter
intake period. The paper recommends more work to examine other
stages of lactation in case this was a lactation stage effect or a
grass effect.

"Another point to consider is that to feed various yeasts and
protected starches and proteins you will need a buffer feed, which
means more feed in the yard, more expense and less time grazing,"
Piers Badnell continues. "More feeding inside leads to a cow that
is less proficient at grazing and thus added direct cost of
production and there are also those hidden extra cost of yard work
etc.

"So from this I conclude it is far less a risk and potential
problem from SARA than alluded to in the articles. Part of the
problem I think comes down to grazing ability and behaviour in the
cow. If a cow has not been trained to graze and therefore chooses
what she eats, does not graze hard and achieve good residuals, she
will just graze the tips of the grass which are the "concentrate
part of the plant," he says.

"They carry high fermentable carbohydrates and low levels of
physical fibre. So the key is good grazing pressure and training
cows to graze to a good residual which all cows can do if grazing
is allocated properly. Taking away cow choice means she then grazes
hard to a good residual and takes in more fibre from the stem. This
means intakes are balances and it helps avoiding the possible
effects of SARA as quoted in the article," Piers Badnell
explains.

"In the paper there also appeared to be a clear herd
effect. Some herds had cows with SARA and some herds had no
or very small number of cows with SARA. Also when comparing
between cows with or without SARA signs there were no clear
differences in terms of performance. There was no
explanation or investigation as to if there was a difference in
management of the herds and whether this had an
influence. Also when comparing between cows with or without
SARA signs there were no clear differences in terms of performance.
But what this does signify is you can graze cows and not get SARA,"
he states.

"Graze properly and you reduce the chances of problems. Read the
paper itself and look out for the symptoms in the cows. If you are
grazing properly I think it is unlikely you will find them but if
you do eliminate other possible causes and take action on fact
rather than opinion," he concludes.